Area Forecast Discussion
Issued by NWS Hastings, NE

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000
FXUS63 KGID 180553
AFDGID

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE HASTINGS NE
1153 PM CST WED DEC 17 2014

.UPDATE...
ISSUED AT 825 PM CST WED DEC 17 2014

CANNOT RULE OUT A SLIGHT CHANCE FOR LIGHT FREEZING DRIZZLE UNTIL
AROUND 06Z BEFORE BETTER SATURATION OCCURS AND PCPN TRANSITIONS TO
LIGHT SNOW. HAVE EXPANDED FZDZ POTENTIAL TO OUR OUR ENTIRE CWA
FOR A FEW HOURS. CURRENT WINTER WX ADVISORY STILL LOOKS ON TRACK
ATTM.

&&

.SHORT TERM...(THIS EVENING THROUGH THURSDAY)
ISSUED AT 314 PM CST WED DEC 17 2014

AN UPPER LEVEL DISTURBANCE LIFTING FROM THE SOUTHERN ROCKIES INTO
THE CENTRAL PLAINS WILL SPREAD LIGHT SNOWFALL ACROSS MUCH OF THE
LOCAL AREA OVERNIGHT. THIS DISTURBANCE WILL THEN RAPIDLY TRACK
EAST DURING THE DAY ON THURSDAY...WITH A BRIEF PERIOD OF FREEZING
DRIZZLE POSSIBLE DURING THE MORNING HOURS TOMORROW ON THE
BACKSIDE OF THIS DISTURBANCE.

FOR TONIGHT...EXPECT THE SHOWER ACTIVITY ACROSS SOUTHERN KANSAS
THIS AFTERNOON TO CONTINUE TO SPREAD NORTHWARD...WITH LIGHT
SNOWFALL EXPECTED TO BECOME LIKELY ACROSS MUCH OF NORTH CENTRAL
KANSAS DURING THE EVENING HOURS. WHILE THE BRUNT OF THE FORCING
FROM THE UPPER LEVEL DISTURBANCE WILL BE FOCUSED SOUTH AND EAST OF
THE LOCAL AREA...CONTINUE TO EXPECT SOME SMALL ACCUMULATIONS
MAINLY ACROSS THE SOUTHEASTERN HALF OF THE LOCAL AREA...WITH A
SHARP GRADIENT EXPECTED THE FURTHER YOU WORK NORTHWEST. AS A
RESULT...ATTEMPTED TO FINE TUNE THE FORECAST SOME...INCREASING
TOTALS A BIT ACROSS THE ADVISED AREA...AND DECREASING THEM BY
ABOUT HALF ACROSS MOST OF OUR NEBRASKA COUNTIES.

OTHER THAN ADJUSTING SNOWFALL AMOUNTS...THE LARGEST CHANGE TO THE
SHORT TERM PORTION OF THE FORECAST WAS TO REDUCE THE COVERAGE OF
FREEZING DRIZZLE...AS CONFIDENCE FOR IT BEING REALIZED...AT LEAST
DURING THE OVERNIGHT HOURS...IS EXTREMELY LOW. WHILE AREAS TO OUR
WEST AND SOUTHWEST SAW SOME LIGHT DRIZZLE ACCUMULATIONS THIS
AFTERNOON...CALLS TO WESTERN PORTIONS OF OUR FORECAST AREA THIS
AFTERNOON HAVE LED US TO BELIEVE THAT THE SURFACE DEWPOINT
SPREADS ARE TOO GREAT ACROSS OUR LOCAL AREA FOR THE LIGHT RETURNS
ON RADAR TO BE REACHING THE GROUND. THEN...AS THE MID LEVELS OF
THE ATMOSPHERE BEGIN TO SATURATE OVERNIGHT WITH THE APPROACHING
DISTURBANCE...HAVE A DIFFICULT TIME SEEING FREEZING DRIZZLE WILL
BE ABLE TO DEVELOP GIVEN THE MODELED SOUNDINGS. HENCE...DECIDED TO
REMOVE DRIZZLE THROUGH MOST OF THE OVERNIGHT HOURS. THAT
SAID...DID KEEP SOME DRIZZLE IN THE FORECAST AREA ON THE TAIL END
OF THE EVENT AS DRY AIR INTRUDES AT THE MID LEVELS...BUT
DEPENDING ON THE AMOUNT OF ACCUMULATING SNOW...THIS MAY HAVE A
VERY MINIMAL IMPACT ON SURFACE CONDITIONS ACROSS THE LOCAL AREA.

OTHERWISE...EXPECT CLOUDY AND SEASONABLY COOL TEMPERATURES OVER
THE NEXT 24 HOURS...WITH LOWS OVERNIGHT NEAR 20 DEGREES...AND
HIGHS ON THURSDAY NEAR 30 THANKS TO THE LINGERING CLOUD COVER
ACROSS THE REGION BEHIND THIS DISTURBANCE.

.LONG TERM...(THURSDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 314 PM CST WED DEC 17 2014

PATTERN: FAIRLY LOW AMPLITUDE FLOW HEADING INTO THIS WEEKEND WILL
MODIFY TO INCREASING AMPLIFICATION AS A TROF DEVELOPS NEAR THE
DATELINE...FORCING SUBTROPICAL HIGH PRES TO BREAK OFF AND SETUP OVER
THE E PAC. THIS WILL RESULT IN A LONGWAVE TROF DEVELOPING OVER THE
CNTRL AND ERN USA NEXT WEEK.

THE PAST 3 RUNS OF THE EC/GFS/GEM ARE IN OUTSTANDING AGREEMENT WITH
EACH OTHER AND THEIR ENSEMBLE MEANS...AS WELL AS THE LAST 2 UKMET
RUNS...REGARDING THE LARGE-SCALE PATTERN/LONGWAVE FLOW. THIS
SUGGESTS ABOVE NORMAL PREDICTABILITY.

BOTTOM LINE IS TEMPS WILL GRADUALLY EDGE UPWARD THRU THE WEEKEND
THEN TURNING COLDER...WITH NO MAJOR PRECIP POTENTIAL.

ALOFT: A WEAK SHORTWAVE TROF WILL MOVE THRU FRI NIGHT AND WILL BE OF
LITTLE CONSEQUENCE. THE NEXT SHORTWAVE TROF WILL MOVE THRU SUN JUST
AHEAD OF A STRONG 175 KT ANTICYCLONICALLY-CURVED JET STREAK. THE
ASSOCIATED POTENT SHORTWAVE TROF WILL BE CROSSING THE NRN ROCKIES
SUN AND DIVE INTO THE PLAINS MON...SLOWING DOWN WITH THE
AMPLIFICATION AND CLOSING OFF AND MID-LVL LOW. NNW FLOW WILL MOVE
IN TUE-WED WITH RISING HEIGHTS AS THE NEXT TROF APPROACHES THE PAC
NW COAST.

SURFACE: HIGH PRES WILL BE OVER THE GREAT LAKES FRI AND GRADUALLY
SLIP E INTO SAT...AS A WEAK LOW FORMS OVER ALBERTA AND EJECTS ONTO
THE CANADIAN PRAIRIES. A WEAK WARM FRONT WILL TRY TO DEVELOP AND
EXTEND SOUTHWARD INTO THE CNTRL PLAINS. STRONGER LOW PRES SHOULD
THEN FORM OVER ALBERTA SUN AND DIVE SE INTO THE NRN PLAINS MON
...WITH THE INITIAL LOW FADING. ITS ASSOCIATED COLD FRONT WILL CROSS
THE CNTRL PLAINS MON. HIGH PRES SHOULD FOLLOW TUE-WED.

THE DAILY DETAILS...

THU NIGHT-SAT: PERSISTENCE SEEMS WISE AS GFS/NAM CROSS SECTIONS HAVE
A LOW STRATUS SIGNAL. IT HAS BEEN IMPOSSIBLE TO DISLODGE THE PAST
SEVERAL DAYS...EVEN AFTER THE LOW THAT MOVED THRU HERE SUN. IT DOES
APPEAR THE WRN EDGE WILL BE CLOSE TO THE WRN FRINGE OF THE FCST AREA
/NEAR HWY 283/ THRU FRI. DOES THE STRATUS LINGER INTO SAT FOR ALL OR
PART OF THE FCST AREA? CONFIDENCE IS VERY LOW ON IF/WHEN/WHERE
STRATUS REMAINS OR DEPARTS BUT WE HAVE INDICATED GRADUAL IMPROVEMENT
FROM THE W FRI NIGHT INTO SAT.

THE PREVIOUS SHIFT INSERTED A SLIGHT CHANCE OF FRZG DRZL THU NIGHT
INTO FRI MORNING. WE AS FCSTRS HAVE VERY LITTLE SKILL IN FORECASTING
FRZG DRZL AND THE FCST MOISTURE DEPTH APPEARS TOO SHALLOW TO ME
BASED ON PAST EXPERIENCE...BUT LOOK AT THE 12Z LBF SOUNDING THIS AM.
THEY HAVE BEEN DEALING WITH IT W OF HERE TODAY. SO IT HAS BEEN
EXPANDED FROM 6 PM THU-12 PM FRI...BUT IT IS JUST A SLIGHT CHANCE.
CONFIDENCE IS LOW.

STRATUS ALWAYS HAS SIGNIFICANT IMPLICATIONS FOR TEMPS. THAT MEANS
THERE IS SIGNIFICANT BUST POTENTIAL WHERE IT LINGERS AND WE DONT
HAVE IT OR WHERE IT CLEARS AND WE DO.

SUN: PARTLY-MOSTLY CLOUDY. IT COULD BE SURPRISINGLY WARM DEPENDENT
ON CLOUD COVER.

SUN NIGHT: POSSIBLY A NARROW/SMALL ARC OF BROKEN SHWRS WITH A PRE-
FRONTAL TROF.

MON: A COUPLE MORE BRIEF SHWRS WITH COLD FRONTAL PASSAGE.

TUE: NW WINDS CRANK IN COLD AIR ADVECTION. COULD SEE A LITTLE WRAP-
AROUND LIGHT SNOW ON THE BACKSIDE OF THE DIMINISHING LOW OVER IA.
ANY SNOWFALL WILL NOT BE A BIG DEAL. THE MID-LVL CIRCULATION IS
CURRENTLY FCST TO REMAIN N OF THE FCST AREA AND THIS IS NOT GOOD FOR
DECENT PRECIP HERE.

WED: ANOTHER DAY IN THE COLD SECTOR AS A POTENTIALLY INTENSE /SUB
980/ LOW CRANKS OVER THE GREAT LAKES.

&&

.AVIATION...(FOR THE 06Z KGRI/KEAR TAFS THROUGH 06Z THURSDAY NIGHT)
ISSUED AT 1152 PM CST WED DEC 17 2014

YET AGAIN...ANOTHER TAF PERIOD WITH A SOMEWHAT CHALLENGING/TRICKY
FORECAST REGARDING MAINLY CEILING TRENDS...BUT POSSIBLY VISIBILITY
AS WELL. ON TOP OF THIS...AT LEAST A BRIEF PERIOD OF LIGHT
SNOW IS LIKELY RIGHT AWAY DURING THESE FIRST 6 HOURS EARLY THIS
MORNING...WITH AMOUNTS LIKELY AVERAGING LESS THAN ONE-HALF INCH.
ALTHOUGH NOT INDICATED IN THE TAFS DUE TO LACK OF CONFIDENCE IN
COVERAGE/OCCURRENCE...A BRIEF PERIOD OF LIGHT FREEZING DRIZZLE
CANNOT BE RULED AS WELL. SO...THE BOTTOM LINE IS THAT CEILING-
WISE...DESPITE SOME MODELS/GUIDANCE SUGGESTING A RETURN TO
PREVAILING VFR THROUGH MUCH OF THE LATTER HALF OF THE
PERIOD...HAVE INSTEAD MAINTAINED A MORE PESSIMISTIC ROUTE AS
SUGGESTED BY OTHER MODELS/GUIDANCE AND THE PREVIOUS
FORECAST...WITH A COMBINATION OF MVFR/IFR CEILING PERSISTING
THROUGH NEARLY THE ENTIRE PERIOD. VISIBILITY WISE...ALTHOUGH SOME
LIGHT FOG COULD BECOME A FACTOR...FOR NOW HAVE ONLY INDICATED
SUB-VFR CONDITIONS IN ASSOCIATION WITH ANY FALLING SNOW DURING
THE FIRST SEVERAL HOURS. FORTUNATELY...SURFACE WINDS WILL NOT BE A
MAJOR AVIATION ISSUE THROUGH THE PERIOD...WITH SUSTAINED SPEEDS
AVERAGING UNDER 10KT THROUGHOUT...AS DIRECTION TRANSITIONS FROM
EASTERLY TO SOUTHERLY.

&&

.GID WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
KS...WINTER WEATHER ADVISORY UNTIL 9 AM CST THURSDAY FOR KSZ007-018-
     019.

&&

$$

UPDATE...FAY
SHORT TERM...ROSSI
LONG TERM...HALBLAUB
AVIATION...PFANNKUCH


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